In the oil and gas exploration industry, marine geophysical surveying is commonly used in the search for hydrocarbon-bearing subterranean formations. Marine geophysical surveying techniques may yield knowledge of the subsurface structure of the Earth, which is useful for finding and extracting hydrocarbon deposits such as oil and natural gas. Seismic surveying is one of the well-known techniques of marine geophysical surveying.
In some instances of seismic surveying conducted in a marine environment (which may include saltwater, freshwater, and/or brackish water environments), one or more seismic sources are typically configured to be submerged and towed by a vessel. The vessel is typically also configured to tow one or more laterally spaced streamers through the water. In some instances, in addition to or in lieu of streamers, sensors may be located at or near the seafloor, either on ocean bottom cables or nodes. At selected times, control equipment may cause the one or more seismic sources to actuate. Seismic signals may then be received by sensors such as hydrophones disposed along the streamers. Data collected during such a seismic survey may be analyzed to assist identification of hydrocarbon-bearing geological structures, and thus determine where deposits of oil and natural gas may be located.
In some cases, hydrophones may also be used in seafloor reservoir monitoring (e.g., permanent reservoir monitoring or PRM) applications. For example, hydrophones may be disposed on the seafloor to record data while seismic sources (e.g., seismic sources at or near the water surface) are actuated.
This specification includes references to “one embodiment” or “an embodiment.” The appearances of the phrases “in one embodiment” or “in an embodiment” do not necessarily refer to the same embodiment. Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure.
Various devices, units, circuits, or other components may be described or claimed as “configured to,” “usable to,” or “operable to” perform a task or tasks. In such contexts, “configured to,” “usable to,” and “operable to” are each used to connote structure by indicating that the devices/units/circuits/components include structure that performs the task or tasks during operation. As such, the device/unit/circuit/component can be said to be configured to, usable to, or usable to perform the task even when the specified device/unit/circuit/component is not currently operational (e.g., is not on or in operation). The devices/units/circuits/components used with the “configured to,” “usable to,” or “operable to” language may include electronic hardware—for example, circuits, memory storing program instructions executable to implement the operation, etc.—mechanical devices, or other types of structure. Reciting that a device/unit/circuit/component is “configured to,” “usable to,” or “operable to” perform one or more tasks is expressly intended not to invoke 35 U.S.C. §112(f), for that device/unit/circuit/component.
In some embodiments, various items of information relating to seismic surveying, such as data collected by hydrophones, may be embodied in a geophysical data product. A “geophysical data product” may be stored on a computer-readable, non-transitory medium and may embody geophysical data (such as raw streamer data, processed streamer data, two- or three-dimensional maps based on streamer data, etc.). Some non-limiting examples of computer-readable media may include hard drives, CDs, DVDs, print-outs, etc. In some embodiments, raw analog data from streamers may be stored as a geophysical data product. In other instances, the data may first be digitized and/or conditioned prior to being stored as the geophysical data product. In yet other instances, the data may be fully processed into a two- or three-dimensional map of the various geophysical structures before being stored in the geophysical data product. The geophysical data product may be produced offshore (e.g., by equipment on a vessel) or onshore (e.g., at a facility on land) either within the United States or in another country. If the geophysical data product is produced offshore or in another country, it may be imported onshore to a facility in the United States. Once onshore in the United States, geophysical analysis may be performed on the geophysical data product.
In some instances of a typical marine geophysical survey, one or more seismic sources may be used to generate seismic energy. Various types of seismic sources may be used for this purpose. For example (and without limitation), air guns, flexural disc projectors, and/or marine vibrators may be used in some cases. The seismic energy may travel downward through the water and through the formations underlying the water bottom. Impedance boundaries within the subsea formations may reflect (at least in part) the seismic energy that travels through such formations. The reflected seismic energy may then travel upwards. Seismic sensors (e.g., hydrophones, geophones, accelerometers, etc.) located in the vicinity of the formation may capture such reflected seismic energy. These seismic sensors may convert the captured seismic energy into signals, such as optical or electrical signals. The electrical or optical signals may then be interpreted to provide information as to the composition and/or structure of the various subsurface formations under the water bottom. Such information may be used, for example, to determine the possibility that such formations may contain mineral deposits including hydrocarbons.